Academic literature on the topic 'Stem heating model'
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Journal articles on the topic "Stem heating model"
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Jones, Joshua L., Brent W. Webb, Bret W. Butler, Matthew B. Dickinson, Daniel Jimenez, James Reardon, and Anthony S. Bova. "Prediction and measurement of thermally induced cambial tissue necrosis in tree stems." International Journal of Wildland Fire 15, no. 1 (2006): 3. http://dx.doi.org/10.1071/wf05017.
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A model for fire-induced heating in tree stems is linked to a recently reported model for tissue necrosis. The combined model produces cambial tissue necrosis predictions in a tree stem as a function of heating rate, heating time, tree species, and stem diameter. Model accuracy is evaluated by comparison with experimental measurements in two hardwood and two softwood species: red maple (Acer rubrum), chestnut oak (Quercus prinus), ponderosa pine (Pinus ponderosa), and Douglas-fir (Pseudotsuga menziesii). Results are promising, and indicate that the model predicts stem mortality/survival correctly in ~75–80% of the test cases. A limited sensitivity analysis of model kill depth predictions suggests that the model is more sensitive to required input data for some species than for others, and that the certainty in predicting vascular cambium necrosis decreases as stem diameter decreases.
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Jones, Joshua L., Brent W. Webb, Dan Jimenez, James Reardon, and Bret Butler. "Development of an advanced one-dimensional stem heating model for application in surface fires." Canadian Journal of Forest Research 34, no. 1 (January 1, 2004): 20–30. http://dx.doi.org/10.1139/x03-187.
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A new one-dimensional heat conduction model for predicting stem heating during fires is presented. The model makes use of moisture- and temperature-dependent thermal properties for layers of bark and wood. The thermal aspects of the processes of bark swelling, desiccation, and devolatilization are treated in an approximate fashion. An energy balance reveals that simulation with a heat flux input boundary condition requires that these phenomena be accounted for. Previous models have used temperaturetime boundary conditions, which prevents them from being used in conjunction with fire behavior models. This model uses a fluxtime profile for its boundary condition, making it possible to eventually couple it to fire behavior models. The model was developed and validated with laboratory experiments on Douglas-fir (Pseudotsuga menziesii (Mirb.) Franco) samples. It is intended that this model be used in conjunction with fire behavior and cell mortality models to make predictions of stem heating related mortality before prescribed burns.
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Wei, Rui, Guang Yang, Jili Zhang, Xiaohong Wang, and Xin Zhou. "The thermal insulation properties of oak (Quercus mongolica) bark and the applicability of stem heating models." International Journal of Wildland Fire 28, no. 12 (2019): 969. http://dx.doi.org/10.1071/wf18232.
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The survival probability of a tree exposed to surface fire varies widely depending on its bark. To advance the understanding of insulation properties of bark, mean thickness (BT), moisture content (MCb), surface structure (BS) and density (ρb) of bark samples of Mongolian oak (Quercus mongolica) (n=395) for four diameter classes were investigated. In addition, data from 158 heating experiments simulating low-intensity surface fires in the laboratory were used to assess the relative importance of these properties affecting thermal insulation and evaluate the applicability of two stem heating models, an analytical, one-dimensional model and the FireStem2D model. Overall, BT is the best predictor of bark insulation capacity and MCb only contributes significantly to explain the residence time of cambial temperature >60°C (τ>60), whereas ρb and BS have minor effects. Although the two stem heating models overestimate the time required for cambium temperatures to reach 60°C (τ60), FireStem2D performed better than analytical model. Furthermore, FireStem2D provides good predictions of τ>60 and maximal cambial temperature (Tmax). In addition, errors in FireStem2D may be driven mainly by the errors in temperature measurement and the limitation of a two-dimensional model. The study provides a better knowledge of interactions between bark properties and heat transfer, which may improve the predictability of fire-caused stem injury for Mongolian oak and other species with similar bark properties.
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Bova, Anthony S., and Matthew B. Dickinson. "An inverse method to estimate stem surface heat flux in wildland fires." International Journal of Wildland Fire 18, no. 6 (2009): 711. http://dx.doi.org/10.1071/wf07122.
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Models of wildland fire-induced stem heating and tissue necrosis require accurate estimates of inward heat flux at the bark surface. Thermocouple probes or heat flux sensors placed at a stem surface do not mimic the thermal response of tree bark to flames. We show that data from thin thermocouple probes inserted just below the bark can be used, by means of a one-dimensional inverse heat conduction method, to estimate net heat flux (inward minus outward heat flow) and temperature at the bark surface. Further, we estimate outward heat flux from emitted water vapor and bark surface re-radiation. Estimates of surface heat flux and temperature made by the inverse method confirm that surface-mounted heat flux sensors and thermocouple probes overestimate surface heat flux and temperature. As a demonstration of the utility of the method, we characterized uneven stem heating, due to leeward, flame-driven vortices, in a prescribed surface fire. Advantages of using an inverse method include lower cost, ease of multipoint measurements and negligible effects on the target stem. Drawbacks of the simple inverse model described herein include inability to estimate heat flux in very moist bark and uncertainty in estimates when extensive charring occurs.
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Potter, Brian E., and Jeffrey A. Andresen. "A finite-difference model of temperatures and heat flow within a tree stem." Canadian Journal of Forest Research 32, no. 3 (March 1, 2002): 548–55. http://dx.doi.org/10.1139/x01-226.
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The authors present a finite-difference numerical model of heat flow within a horizontal section of a tree stem. Processes included in the model are solar radiative heating, infrared emission and absorption, convective heat exchange between tree surface and the atmosphere, and conduction inside the tree. Input variables include wood density, wood thermal conductivity, wood specific heat, wind speed, air temperature, and insolation. The model produces time series of temperature for grid points inside the tree stem. Based on comparison with observations from two case studies, the model appears capable of reproducing relative timing and amplitude of temperature patterns at the cardinal aspects. Sensitivity tests show that insolation and convection parameters, as well as the physical properties of the tree, can all have a strong influence on model results.
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Barthakur, NN, and NP Arnold. "A Transient Method for Determining Thermal Diffusivity of Tobacco Stems." Beiträge zur Tabakforschung International/Contributions to Tobacco Research 14, no. 5 (October 1, 1989): 321–26. http://dx.doi.org/10.2478/cttr-2013-0609.
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AbstractA microwave generator and a closed-circuit wind tunnel were used to measure the thermal diffusivity of tobacco (Nicotianatabacum L.) stems in vivo by the unsteady-state method. A simple mathematical model for heat flow, based on Fourier's heat-conduction equation and Newton's law of cooling, was used in this study. The microwave method was found to be relatively rapid as both heating and cooling of a cylindrical stem in an air stream could be completed in approximately 30 minutes for thermal-diffusivity determinations. Thermal-diffusivity value of the tobacco stems, containing 94 % moisture and a mean stem temperature of 30°C, was found to be (1.38 ± 0.06) × 10-7 m2 s-1. The coefficient of variation for the measurements did not exceed 1.4 % as determined through the analysis of cooling curves for five different air-flow rates over the stems. This study showed that the microwave technique could be effectively used to determine both accurately and reliably the thermal diffusivity of tobacco stems in vivo.
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Gu, Tianbao, Torsten Berning, and Chungen Yin. "Application of a New Statistical Model for the Description of Solid Fuel Decomposition in the Analysis of Artemisia apiacea Pyrolysis." Energies 14, no. 18 (September 14, 2021): 5789. http://dx.doi.org/10.3390/en14185789.
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Pyrolysis, one of the key thermochemical conversion technologies, is very promising to obtain char, oil and combustible gases from solid fuels. Kinetic modeling is a crucial method for the prediction of the solid conversion rate and analysis of the pyrolysis process. We recently developed a new statistical model for the universal description of solid fuel decomposition, which shows great potential in studying solid fuel pyrolysis. This paper demonstrates three essential applications of this new model in the analysis of Artemisia apiacea pyrolysis, i.e., identification of the conversion rate peak position, determination of the reaction mechanism, and evaluation of the kinetics. The results of the first application show a very good agreement with the experimental data. From the second application, the 3D diffusion-Jander reaction model is considered as the most suitable reaction mechanism for the description of Artemisia stem pyrolysis. The third application evaluates the kinetics of Artemisia stem pyrolysis. The evaluated kinetics vary with the conversion degree and heating rates, in which the activation energies and pre-exponential factors (i.e., lnA vs. Ea) show a linear relationship, regardless of the conversion and heating rates. Moreover, the prediction of the conversion rate using the obtained kinetics shows an excellent fit with the experimental data.
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Tseng, Ling-Shu, Sheng-Hsien Chen, Mao-Tsun Lin, and Ying-Chu Lin. "Umbilical Cord Blood-Derived Stem Cells Improve Heat Tolerance and Hypothalamic Damage in Heat Stressed Mice." BioMed Research International 2014 (2014): 1–8. http://dx.doi.org/10.1155/2014/685683.
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Heatstroke is characterized by excessive hyperthermia associated with systemic inflammatory responses, which leads to multiple organ failure, in which brain disorders predominate. This definition can be almost fulfilled by a mouse model of heatstroke used in the present study. Unanesthetized mice were exposed to whole body heating (41.2°C for 1 hour) and then returned to room temperature (26°C) for recovery. Immediately after termination of whole body heating, heated mice displayed excessive hyperthermia (body core temperature ~42.5°C). Four hours after termination of heat stress, heated mice displayed (i) systemic inflammation; (ii) ischemic, hypoxic, and oxidative damage to the hypothalamus; (iii) hypothalamo-pituitary-adrenocortical axis impairment (reflected by plasma levels of both adrenocorticotrophic-hormone and corticosterone); (iv) decreased fractional survival; and (v) thermoregulatory deficits (e.g., they became hypothermia when they were exposed to room temperature). These heatstroke reactions can be significantly attenuated by human umbilical cord blood-derived CD34+cells therapy. Our data suggest that human umbilical cord blood-derived stem cells therapy may improve outcomes of heatstroke in mice by reducing systemic inflammation as well as hypothalamo-pituitary-adrenocortical axis impairment.
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Joswiak, David J. "Height Measurement of Interplanetary Dust Particles by Scanning Transmission Electron Microscopy (STEM)." Microscopy Today 8, no. 6 (August 2000): 46–49. http://dx.doi.org/10.1017/s1551929500052883.
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Interplanetary dust particles (IDPs) comprise an important source of extraterrestrial materials available for study of our solar system and originate from either the asteroid belt or from short period comets. IDPs from cometary sources are particularly important as they constitute the only physical samples of comets available; all known meteorites are derived from the asteroids, the Moon or Mars. By measuring the densities of IDPs and using an appropriate atmospheric entry heating model, it is possible to determine whether an individual IDP has been derived from an asteraidal or cometary source region. Calculating the density of an IDP requires knowledge of both its mass and volume, which can be determined by using a combination of secondary and transmission electron microscopy techniques. We have developed methods to measure both of these parameters and thus routinely measure densities for individual IDPS in the size range of 5-15 μm.
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Giusti, Ruggero, and Giovanni Lucchetta. "Modeling the Adhesion Bonding Strength in Injection Overmolding of Polypropylene Parts." Polymers 12, no. 9 (September 10, 2020): 2063. http://dx.doi.org/10.3390/polym12092063.
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In this work, the bonding strength of overmolded polypropylene is investigated and modeled. A T-joint specimen was designed to replicate the bonding between a base and an overmolded stem made of the same polymer: a previously molded plaque was used for the base, and the stem was directly overmolded. The effect of melt temperature, holding pressure, and localized heating was investigated following the design of experiments approach. Both the melt and base temperature positively affect the welding strength. On the contrary, the holding pressure negatively contributed, as the crystallization temperature significantly increases with pressure. Then, the bonding strength of the specimens was predicted using a non-isothermal healing model. Moreover, the quadratic distance of diffusion (based on the self-diffusion model) was calculated and correlated with the bonding strength prediction. The non-isothermal healing model well predicts the bonding strength when the reptation time is calculated within the first 0.09 s of the interface temperature evolution. The prediction error ranges from 1% to 35% for the specimens overmolded at high and low melt and base temperatures, respectively.
Dissertations / Theses on the topic "Stem heating model"
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Jones, Joshua Levi. "Development of an advanced stem heating model /." Diss., CLICK HERE for online access, 2003. http://contentdm.lib.byu.edu/ETD/image/etd231.pdf.
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Jones, Joshua L. "Development of an Advanced Stem Heating Model." BYU ScholarsArchive, 2003. https://scholarsarchive.byu.edu/etd/88.
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A new one-dimensional heat conduction model for predicting stem heating during fires is presented. The model makes use of moisture and temperature dependent thermal properties for bark and wood. Also, the thermal aspects of the processes of bark swelling, desiccation, and devolatilization are treated in an approximate fashion. Simulation with a surface flux boundary condition requires that these phenomena be accounted for. Previous models have used temperature-time boundary conditions, which prevents them from being directly coupled to fire behavior models. This model uses a flux-time profile for its boundary condition, making it possible to eventually couple it to fire behavior models. Cambial mortality predictions are made through the incorporation of a cell mortality model. The model was developed and validated with laboratory experiments on four species.
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Wu, Haijun Walker Paul N. "Numerical model for isobaric steam heating of initially saturated packed beds." [University Park, Pa.] : Pennsylvania State University, 2009. http://etda.libraries.psu.edu/theses/approved/WorldWideIndex/ETD-4300/index.html.
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Venturi, Elisa. "Dynamic simulation and analysis of a Passive House case study with direct PV system for heating and domestic hot water production." Master's thesis, Alma Mater Studiorum - Università di Bologna, 2018. http://amslaurea.unibo.it/16590/.
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Different heating systems for space heating and domestic hot water (DHW) preparation are investigated with respect to their energy efficiency. In particular, a case study of a multi-storey Passive House (called An-der-Lan) is analysed by means of dynamic simulations.
The first part of dynamic simulations focuses on the comparison of the UA and RC models for a simple office located in Rome. This is a case study from the project IEA SHC T56 – System Simulation Models. In particular, attention is put on the influence of the thermal capacity. Assuming the RC model as the reference case, variants of the UA model with different percentages of the thermal capacity are simulated, in order to find out the most similar to the RC model. The same investigation is carried out for the An-der-Lan building. In general, it is not possible to identify the best UA model, because for every considered quantity, the minimum difference between the UA and RC model is got for a different percentage of the thermal mass.
The second part of dynamic simulation focuses on the comparison among different systems for heating and DHW preparation. The realized system is direct electric heating for both space heating and DHW preparation. It is denoted as the reference Case1 and it is compared against alternative solutions. Case2 is based on a central air/water heat pump system for both heating and DHW production. A sensitivity analysis study is conducted. Finally, Case3 and Case4 are a mix of the previous two cases.
Results show that Case2 is the best in terms of electric energy required from the grid, although it is the system with the highest thermal losses. Furthermore, the PV system only in the south façade is not sufficient to cover the energy required in neither of the cases.
Finally, annual, monthly, daily, hourly and 10 minutes balances are compared. Results show the importance of smaller time step in balances between required and produced energy, in order to have more precise results.
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Pic, Axel. "Numerical and experimental investigations of self-heating phenomena in 3D Hybrid Bonding imaging technologies." Thesis, Lyon, 2019. http://www.theses.fr/2019LYSEI054.
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Dans cette thèse, les phénomènes d’auto-échauffement ont été étudié pour guider la conception de circuits intégrés 3D de nouvelle génération. Grâce à des études expérimentales et numériques, la dissipation thermique dans des imageurs 3D par collage hybride a été analysée et l’impact de l’augmentation de température résultante a été évalué. Premièrement, afin de développer des modèles précis, les propriétés thermiques des matériaux utilisés dans les circuits intégrés ont dû être déterminées. Différents films minces diélectriques impliquant des oxydes, des nitrures et des composés low-k ont été étudiés. Pour ce faire, la microscopie thermique à sonde locale (SThM) et la méthode électrothermique 3ω, sensibles à la conductivité thermique effective faible et élevée, ont été mises en œuvre. Dans un deuxième temps, des modèles éléments finis de circuits intégrés 3D ont été développés. Une méthode numérique nécessitant homogénéisations et approches multi-échelles a été proposée pour surmonter des grands rapports de forme inhérents à la microélectronique. La procédure numérique a été validée en comparant les calculs et les mesures expérimentales effectuées par SThM, la thermométrie résistive et la microscopie infrarouge sur une puce de test par collage hybride simplifiée. Il a été montré que la dissipation de chaleur est principalement limitée par la conductance du puit thermique ainsi que les pertes par l'air. Enfin, des études numériques et expérimentales ont été réalisées sur des imageurs 3D par collage hybride fonctionnels. Le champ de température a été mesuré par SThM et comparé aux calculs par éléments finis à la surface de la matrice. Les résultats numériques ont montré que la température de la surface des pixels est égale à celle du Front-End-Of-Line de l’imageur. L'influence de l'échauffement sur les performances optiques de l'imageur a été déduite de cette analyse. Cette étude a permis également d'évaluer les différentes méthodes numériques et expérimentales pour la caractérisation de la dissipation de chaleur en microélectroniqueIn this PhD thesis, self-heating phenomena are studied for guiding the design of next-generation 3D Integrated Circuits (ICs). By means of experimental and numerical investigations, associated heat dissipation in 3D Hybrid Bonding imagers is analyzed and the impact of the resulting temperature rise is evaluated. First, in order to develop accurate models, the thermal properties of materials used in ICs are to be determined. Different dielectric thin films involving oxides, nitrides, and low-k compounds are investigated. To do so, Scanning Thermal Microscopy (SThM) and the 3ω electrothermal method, sensitive to low and large effective thermal conductivity, are implemented. In a second step, finiteelement models of 3D ICs are developed. A numerical method involving homogenization and a multiscale approach is proposed to overcome the large aspect ratios inherent in microelectronics. The numerical procedure is validated by comparing calculations and experimental measurements performed with SThM, resistive thermometry and infrared microscopy on a simplified Hybrid Bonding test chip. It is shown that heat dissipation is mainly limited by the heat sink conductance and the losses through air. Finally, numerical and experimental studies are performed on fully-functional 3D Hybrid Bonding imagers. The temperature field is measured with SThM and compared with finite-element computations at the die surface. The numerical results show that the temperature of the pixel surface is equal to that of the imager Front-End-Of-Line. The influence of the temperature rise on the optical performance of the imager is deduced from the analysis. The study also allows assessing the various numerical and experimental methods for characterizing heat dissipation in microelectronics
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Yan, Haoheng. "From Mouse Mammary Tumor Model to New Therapeutic Method ---Mammary Tumor Development in Balb/c-Trp53+/- Mice and Magnetic Nanoparticle Induced Heating for Cancer Treatment." 2010. https://scholarworks.umass.edu/dissertations/AAI3409670.
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Mutation and loss of p53 function are common features among human breast cancers. We use BALB/c-Trp53+/- mice as a model to examine the sequence of events leading to mammary tumors. Mammary epithelium proliferation rates were similar in both BALB/c-Trp53+/- mice and wild type controls. Among the 28 mammary tumors collected from BALB/c- Trp53+/- mice, loss of heterozygosity for Trp53 was detected in more than 90% of invasive mammary tumors. Transplantation of Trp53+/- ductal hyperplasias indicated an association between loss of the wild type allele of Trp53 and progression to invasive carcinomas. Expression of biomarkers such as ERα, PR, Her2/Neu and activated Notch1 varied among the tumors suggesting that multiple oncogenic events collaborate with loss of p53 function. The majority of the tumors expressed both luminal and basal cytokeratins (59%). Gene expression analysis showed ligands and receptors of stem cell related pathways, such as Notch and Wnt, were increased in the tumors. These results indicate that mammary tumors in BALB/c Trp53+/- mice might initiate from bipotent mammary progenitor cells. Using magnetic nanoparticles for cancer thermotherapy. Alternating magnetic field (AMF) heating of magnetic nanomaterials provides a promising method for executing therapeutic thermal treatment for cancer patients. In order to explore the potential of magnetic nanoparticles (MNPs) for hyperthermia treatment, we synthesized iron oxide MNPs with various passivation by citric acid, folate, trimethylamine carboxylic acid, or albumin. The albumin passivated MNP (MNP-A) surpassed other MNPs, showing efficient heating with very low inherent cytotoxicity. Confocal microscopy located MNP-A (FITC tagged) accumulation in both cell nucleus and cytosol after 24hr incubation with HeLa cells. The quantity of cell bound MNP-A (including internalized and cell membrane bound MNP-A) was positively associated with MNP-A concentration and incubation time with cells. The MNP-A bound to cells was sufficient to increase the temperature in the cell pellet Δ7°C after 8min exposure to AMF. No significant temperature increase or cell death was detected in control groups. Our data demonstrate that MNP-A provides a selective tool for AMF-induced thermal treatment, as well as useful dosing information for future preclinical animal studies.
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Lashgari, Hamid Reza. "Development of a four-phase thermal-chemical reservoir simulator for heavy oil." Thesis, 2014. http://hdl.handle.net/2152/28477.
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Thermal and chemical recovery processes are important EOR methods used often by the oil and gas industry to improve recovery of heavy oil and high viscous oil reservoirs. Knowledge of underlying mechanisms and their modeling in numerical simulation are crucial for a comprehensive study as well as for an evaluation of field treatment. EOS-compositional, thermal, and blackoil reservoir simulators can handle gas (or steam)/oil/water equilibrium for a compressible multiphase flow. Also, a few three-phase chemical flooding reservoir simulators that have been recently developed can model the oil/water/microemulsion equilibrium state. However, an accurate phase behavior and fluid flow formulations are absent in the literature for the thermal chemical processes to capture four-phase equilibrium. On the other hand, numerical simulation of such four-phase model with complex phase behavior in the equilibrium condition between coexisting phases (oil/water/microemulsion/gas or steam) is challenging. Inter-phase mass transfer between coexisting phases and adsorption of components on rock should properly be modeled at the different pressure and temperature to conserve volume balance (e.g. vaporization), mass balance (e.g. condensation), and energy balance (e.g. latent heat). Therefore, efforts to study and understand the performance of these EOR processes using numerical simulation treatments are quite necessary and of utmost importance in the petroleum industry. This research focuses on the development of a robust four-phase reservoir simulator with coupled phase behaviors and modeling of different mechanisms pertaining to thermal and chemical recovery methods. Development and implementation of a four-phase thermal-chemical reservoir simulator is quite important in the study as well as the evaluation of an individual or hybrid EOR methods. In this dissertation, a mathematical formulation of multi (pseudo) component, four-phase fluid flow in porous media is developed for mass conservation equation. Subsequently, a new volume balance equation is obtained for pressure of compressible real mixtures. Hence, the pressure equation is derived by extending a black oil model to a pseudo-compositional model for a wide range of components (water, oil, surfactant, polymer, anion, cation, alcohol, and gas). Mass balance equations are then solved for each component in order to compute volumetric concentrations. In this formulation, we consider interphase mass transfer between oil and gas (steam and water) as well as microemulsion and gas (microemulsion and steam). These formulations are derived at reservoir conditions. These new formulations are a set of coupled, nonlinear partial differential equations. The equations are approximated by finite difference methods implemented in a chemical flooding reservoir simulator (UTCHEM), which was a three-phase slightly compressible simulator, using an implicit pressure and an explicit concentration method. In our flow model, a comprehensive phase behavior is required for considering interphase mass transfer and phase tracking. Therefore, a four-phase behavior model is developed for gas (or steam)/ oil/water /microemulsion coexisting at equilibrium. This model represents coupling of the solution gas or steam table methods with Hand’s rule. Hand’s rule is used to capture the equilibrium between surfactant, oil, and water components as a function of salinity and concentrations for oil/water/microemulsion phases. Therefore, interphase mass transfer between gas/oil or steam/water in the presence of the microemulsion phase and the equilibrium between phases are calculated accurately. In this research, the conservation of energy equation is derived from the first law of thermodynamics based on a few assumptions and simplifications for a four-phase fluid flow model. This energy balance equation considers latent heat effect in solving for temperature due to phase change between water and steam. Accordingly, this equation is linearized and then a sequential implicit scheme is used for calculation of temperature. We also implemented the electrical Joule-heating process, where a heavy oil reservoir is heated in-situ by dissipation of electrical energy to reduce the viscosity of oil. In order to model the electrical Joule-heating in the presence of a four-phase fluid flow, Maxwell classical electromagnetism equations are used in this development. The equations are simplified and assumed for low frequency electric field to obtain the conservation of electrical current equation and the Ohm's law. The conservation of electrical current and the Ohm's law are implemented using a finite difference method in a four-phase chemical flooding reservoir simulator (UTCHEM). The Joule heating rate due to dissipation of electrical energy is calculated and added to the energy equation as a source term. Finally, we applied the developed model for solving different case studies. Our simulation results reveal that our models can accurately and successfully model the hybrid thermal chemical processes in comparison to existing models and simulators.text
Book chapters on the topic "Stem heating model"
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"Modeling and Optimization of Parabolic Trough Collector." In Modeling and Optimization of Solar Thermal Systems, 121–46. IGI Global, 2021. http://dx.doi.org/10.4018/978-1-7998-3523-3.ch005.
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Parabolic trough collector (PTC) is a concentrating collector widely used for steam cooking, water heating, and also steam power generation and desalination work. The performance of PTC is strongly depends on its process parameters and is a MCDM problem. Implementation of integrated method, that is, entropy with graph theory and matrix approach (E-GTMA) for modelling and optimization of PTC parameters to improve higher outlet temperature (To), higher heat gain (h), and higher thermal efficiency (ηth), is discussed in this chapter. Investigation results indicate the effectiveness of this technique for multi-objective optimization and determined optimal setting as Test no.10 for PTC. Additionally, parametric and ANOVA analysis is carried out to determine the significance and adequacy of the developed model. Last, validation of the proposed model and verification results is done via confirmatory tests, and tests results show comparable and acceptable w.r.t. experimental results.
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S. Leite, Brenno, Daniel J.O. Ferreira, Sibele A.F. Leite, and Vanessa F.C. Lins. "Numerical and Experimental Analysis of Thermochemical Treatment for the Liquefaction of Lemon Bagasse in a Jacketed Vessel." In Biomass [Working Title]. IntechOpen, 2020. http://dx.doi.org/10.5772/intechopen.94364.
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In this work, it was investigated the time evolution of thermal profile inside a liquefaction vessel and how the temperature and time of reaction influenced liquefaction yield. Liquefaction was performed in two different ways: (1) Experimental Analysis; (2) Numerical 3-D model, using Computational Fluid Dynamics (CFD). Liquefaction was performed using lemon bagasse samples, glycerol and sulphuric acid, as catalyst. Temperature and liquefaction Yield (LY) were measured for different time of reaction (30, 60 and 90 minutes). From experimental data, LY were higher than 70 wt% for 90 minutes reaction. The increase in the temperature inside the reactor occurred due to the conduction and natural convection phenomena. Although the jacketed vessel was fed with steam at 125°C, working conditions allowed the heating of the mixture to less than 100°C. CFD thermal profile was in accordance with experimental data. They showed it was necessary 60 minutes to achieve a steady state of heating in the mixture inside this liquefaction vessel. From CFD transient simulations, it was observed some oscillations and detachment from experimental data, which may be due to changes in fluids properties along the process. Despite this consideration CFD could satisfactory analyse heat transfer in this liquefaction process.
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Goody, R. M., and Y. L. Yung. "Band Models." In Atmospheric Radiation. Oxford University Press, 1989. http://dx.doi.org/10.1093/oso/9780195051346.003.0006.
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Radiative heating calculations in the atmosphere involve four distinguishable scales of frequency. First, there is the comparatively slow variation with frequency of the Planck function and its derivative with respect to temperature. About one-half of the radiation from a black body at terrestrial temperatures lies in a wave number range of 500 cm-1. The second scale is that of the unresolved contour of a band. For atmospheric molecules other than water vapor, the Planck function is effectively constant over a single band; water vapor bands must be divided into sections of the order of 50 cm-1 wide before this is so. For a rotating molecule, the next relevant scale of frequency is that of the spacing between rotation lines, approximately 1-5 cm-1. Finally, there is the monochromatic scale on which the absorption coefficient may be treated as a constant, and for which Lambert’s absorption law is obeyed: of the order of one-fifth of a line width ≃ 2 x 10-2 cm-1 for a gas at atmospheric pressure, down to 2 x 10-4cm-1 for a Doppler line in the middle atmosphere. This step takes us to a division of the frequency scale that, when taken together with other features of the calculation, presents a formidable computation task. Calculations can, of course, be made and are made at this limiting spectral resolution (line-by-line calculations) but, despite the fact that they are technically feasible with modern computers, such calculations are rare and are usually performed to provide a few reference cases. The great majority of investigations make use of averages over many lines, embracing spectral ranges that are small compared to a band contour (narrow-band models), or over complete bands (wide-band models), or over the entire thermal spectrum (emissivity models.) There are a number of reasons for working with spectral averages. Practical considerations are that important classes of laboratory measurements, and most atmospheric observations (e.g., satellite radiometry) are made with some spectral averaging, often comparable to that of narrow-band models.
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Slobodianiuk, Kateryna, and Kateryna Samoilenko. "RESEARCH OF HEAT AND MASS TRANSFER DURING CONVECTIVE DRYING OF COLLOID CAPILLARY-POROUS MATERIALS." In Integration of traditional and innovation processes of development of modern science. Publishing House “Baltija Publishing”, 2020. http://dx.doi.org/10.30525/978-9934-26-021-6-39.
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The article presents a reasonable analysis and relevance of the study of the drying process of vegetable raw materials (colloidal capillary-porous materials). Drying is an energy-intensive industrial process that is defined from a technological point of view: on the one hand by heat and moisture exchange between the body surface and the environment, on the other hand by heating the body and transferring moisture inside it due to the form of moisture. One of the most effective ways to increase the shelf life of food is to dry it to equilibrium humidity. Very important are the technological parameters of the drying regimes, which, when used rationally, are able to preserve the biochemical properties and nutrients of the raw material at a high level in the obtained dry product. The study of dehydration of vegetable raw materials is widely practiced around the world, especially in countries such as Germany, France, USA, Argentina, Hungary, Brazil, Poland, Korea, China, Malaysia. However, the obtained processed products lose their biologically active components and nutrients, and the processing process is energy consuming. Therefore, the problem is relevant and needs an effective solution. In this paper, the kinetics of the drying process, thermogravimetric studies and a mathematical model for colloidal capillary-porous materials of plant origin were analyzed. According to the results of the highlighted research, the process of convective drying of colloidal capillary-porous materials was intensified above 21% due to the use of innovative step regimes. The developed beet-rhubarb composition is a colloidal capillary-porous material that stabilizes and protects at the biochemical level betanin of the beet from the effects of temperature during convective drying, has in comparison with the components of the composition lower heat of dehydration and increased thermal-stability. Prolonged high-temperature exposure causes instant complete destruction of sugars, proteins and other nutrients components. Derivatographic studies have confirmed that the use of the temperature range of 100 ° C in a stepwise mode of 100/60 ° C for the developed soybean-spinach composition is safe for biologically active substances and it is justified by experimental temperature curves. Numerical modeling of heat and mass transfer during convective drying of crushed beets and crushed soybeans using the known model by A.V. Lykov satisfactorily describes the process and can be used to model the convection drying of colloidal capillary-porous materials.
Conference papers on the topic "Stem heating model"
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Angele, Kristian, Mathias Cehlin, Carl-Maikel Ho¨gstro¨m, Ylva Odemark, Mats Henriksson, Hernan Tinoco, Hans Lindqvist, and Bengt Hemstro¨m. "Flow Mixing Inside a Control-Rod Guide Tube: Part II—Experimental Tests and CFD-Simulations." In 18th International Conference on Nuclear Engineering. ASMEDC, 2010. http://dx.doi.org/10.1115/icone18-29689.
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A large number of control rod cracks were detected during the refuelling outage of the twin reactors Oskarshamn 3 and Forsmark 3 in the fall of 2008. The extensive damage investigation finally lead to the restart of both reactors at the end of 2008 under the condition that further studies would be conducted in order to clarify all remaining matters. Also, all control rods were inserted 14% in order to locate the welding region of the control rod stem away from the thermal mixing region of the flow. Unfortunately, this measure led to new cracks a few months later due to a combination of surface finish of the new stems and the changed flow conditions after the partial insertion of the control rods. The experimental evidence reported here shows an increase in the extension of the mixing region and in the intensity of the thermal fluctuations. As a part of the complementary work associated with the restart of the reactors, and to verify the CFD simulations, experimental work of the flow in the annular region formed by the guide tube and control rod stem was carried out. Two full-scale setups were developed, one in a Plexiglass model at atmospheric conditions (in order to be able to visualize the mixing process) and one in a steel model to allow for a higher temperature difference and heating of the control rod guide tube. The experimental results corroborate the general information obtained through CFD simulations, namely that the mixing region between the cold crud-removal flow and warm by-pass flow is perturbed by flow structures coming from above. The process is characterized by low frequent, high amplitude temperature fluctuations. The process is basically hydrodynamic, caused by the downward transport of flow structures originated at the upper bypass inlets. The damping thermal effects through buoyancy is of secondary importance, as also the scaling analysis shows, however a slight damping of the temperature fluctuations can be seen due to natural convection due to a pre-heating of the cold crud-removal flow. The comparison between numerical and experimental results shows a rather good agreement, indicating that experiments with plant conditions are not necessary since, through the existing scaling laws and CFD-calculations, the obtained results may be extrapolated to plant conditions. The problem of conjugate heat transfer has not yet been addressed experimentally since complex and difficult measurements of the heat transfer have to be carried out. This type of measurements constitutes one of the main challenges to be dealt with in the future work.
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Kostenko, Y., D. Veltmann, and S. Hecker. "Steam Turbine Hot Standby: Electrical Pre-Heating Solution." In ASME Turbo Expo 2019: Turbomachinery Technical Conference and Exposition. American Society of Mechanical Engineers, 2019. http://dx.doi.org/10.1115/gt2019-90464.
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Abstract Growing renewable energy generation share causes more irregular and more flexible operational regimes of conventional power plants than in the past. It leads to long periods without dispatch for several days or even weeks. As a consequence, the required pre-heating of the steam turbine leads to an extended power plant start-up time [1]. The current steam turbine Hot Standby Mode (HSM) contributes to a more flexible steam turbine operation and is a part of the Flex-Power Services™ portfolio [2]. HSM prevents the turbine components from cooling via heat supply using an electrical Trace Heating System (THS) after shutdowns [3]. The aim of the HSM is to enable faster start-up time after moderate standstills. HSM functionality can be extended to include the pre-heating option after longer standstills. This paper investigates pre-heating of the steam turbine with an electrical THS. At the beginning, it covers general aspects of flexible fossil power plant operation and point out the advantages of HSM. Afterwards the technology of the trace heating system and its application on steam turbines will be explained. In the next step the transient pre-heating process is analyzed and optimized using FEA, CFD and analytic calculations including validation considerations. Therefor a heat transfer correlation for flexible transient operation of the HSM was developed. A typical large steam turbine with an output of up to 300MW was investigated. Finally the results are summarized and an outlook is given. The results of heat transfer and conduction between and within turbine components are used to enable fast start-ups after long standstills or even outages with the benefit of minimal energy consumption. The solution is available for new apparatus as well as for the modernization of existing installations.
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Ozalp, Nesrin. "Energy Process-Step Model of Hydrogen Production in the US Chemical Industry." In ASME 2008 2nd International Conference on Energy Sustainability collocated with the Heat Transfer, Fluids Engineering, and 3rd Energy Nanotechnology Conferences. ASMEDC, 2008. http://dx.doi.org/10.1115/es2008-54121.
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This paper gives a representative energy process-step model of hydrogen production in the U.S. Chemical Industry based on federal data. There have been prior efforts to create energy process-step models for other industries. However, among all manufacturing industries, creating energy flow models for the U.S. Chemical Industry is the most challenging one due to the complexity of this industry. This paper gives concise comparison of earlier studies and provides thorough description of the methodology to develop energy process-step model for hydrogen production in the U.S. Chemical Industry. Results of the energy process-step model of hydrogen production in the U.S. Chemical Industry show that steam allocations among the end-uses are: 68% to process cooling (steam injection to product combustion gases), 25% to process heating, and 7% to other process use (CO2 converter). The model also shows that the major energy consuming step in hydrogen production is the reformer, which consumes approximately 16 PJ fuel. During the course of this study, the most recent U.S. federal energy database available was for the year 1998. Currently, the most recent available U.S. federal energy database is given for the year 2002 based on the data collected from 15,500 establishments.
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Chen, Jinbo, Haiguang Gong, and Lili Tong. "Analysis of Steam Blocking in a Low Pressure Heating System." In 2013 21st International Conference on Nuclear Engineering. American Society of Mechanical Engineers, 2013. http://dx.doi.org/10.1115/icone21-15118.
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An analytic investigation of the steam blocking in low pressure heating channels was conducted. In this paper, the dynamic model of the vapor-liquid interface is established through the basic conservation equations, and the rupture time of the vapor-liquid interface is predicted based on the Rayleigh-Taylor instability. Subsequently, the steam blocking model considering the steam accumulation and the vapor-liquid interface rupture in geysering flow is established. On these bases, the relative volume and relative pressure of the accumulated steam, the relative acceleration and perturbation intensity of the vapor-liquid interface, the time-varying behavior of the ratio of resistance and buoyancy are obtained. It is found that the accumulated steam basically increases linearly with the time going; The oscillation of the pressure and velocity, which is very large at the beginning time of the steam accumulation, decreases gradually with the continuous steam accumulation; The Reynolds number of the liquid within the rising section is very small at the stagnation state since there is no forced circulation flow, and finally a blockage is engendered in the pipeline with the steam accumulated. The theoretical results are in good agreements with the results obtained by a small-scale experiment. The mechanism model is able to predict the steam blocking property during the geysering flow in heating channels well, and can also establish a theoretical basis for the later analysis of the steam blocking elimination.
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Li Jinhai, Fang Lide, Cao Suosheng, and Kong Xiangjie. "Analysis of dynamic model of heating system after step change of water supply temperature." In 2008 10th International Conference on Control, Automation, Robotics and Vision (ICARCV). IEEE, 2008. http://dx.doi.org/10.1109/icarcv.2008.4795823.
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Nayak, Kali Charan, Nomesh P. Kandaswamy, and Syed Faheemulla. "Leakage and Windage Heating in Stepped Labyrinth Seals." In ASME 2019 Gas Turbine India Conference. American Society of Mechanical Engineers, 2019. http://dx.doi.org/10.1115/gtindia2019-2426.
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Abstract Stepped labyrinth seals are used in multiple locations in the gas turbine with the intent to reduced leakage compared to straight labyrinth seals. However the selection of geometric factors in stepped labyrinth seals is critical to allow lower leakage in its operating envelope. Particularly the step height and axial position during the running condition play a vital role. The influence of these factors on the leakage, swirl development and windage heating in stepped labyrinth seal has not been thoroughly investigated in the previously published work. This paper focuses to study above effects with numerical simulations in a smooth four-fin stepped labyrinth seal. Specifically, a 2D axi-symmetric computational fluid dynamics (CFD) model is developed utilizing commercial finite volume-based software incorporating the standard k-ε turbulence model. Using this model, a broad parametric study is conducted by varying step height, axial position of the knife from the step, radial clearance and pressure ratio for a four-teeth stepped labyrinth seal. It has been observed that the seal leakage reduces with increase in step height to pitch ratio up to 0.35 and with further increase it tails off. The axial position of the tooth has strong influence on the flow structure and swirl development in the seal pocket.
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Kurup, Parthiv, Abhishek Parikh, Jana Möllenkamp, Thomas Beikircher, Alexia Samoli, and Craig Turchi. "SAM Process Heat Model Development and Validation: Liquid-HTF Trough and Direct Steam Generation Linear Focus Systems." In ISES Solar World Conference 2017 and the IEA SHC Solar Heating and Cooling Conference for Buildings and Industry 2017. Freiburg, Germany: International Solar Energy Society, 2017. http://dx.doi.org/10.18086/swc.2017.26.06.
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Toersche, H. A., V. Bakker, A. Molderink, S. Nykamp, J. L. Hurink, and G. J. M. Smit. "Controlling the heating mode of heat pumps with the TRIANA three step methodology." In 2012 IEEE PES Innovative Smart Grid Technologies (ISGT). IEEE, 2012. http://dx.doi.org/10.1109/isgt.2012.6175662.
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Fellerman, Andy S., and Caroline K. Pyke. "Predicting Evaporator Vessel Base Thicknesses From Inspected Heating Coils." In ASME 2016 Pressure Vessels and Piping Conference. American Society of Mechanical Engineers, 2016. http://dx.doi.org/10.1115/pvp2016-63825.
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The Highly Active Liquid Effluent and Storage plant at Sellafield, UK, currently uses three evaporators to reduce the volume of active liquor stored within the facility before being vitrified for long term storage. This liquor is highly corrosive and the lifetime of the evaporators is potentially limited by the corrosion loss from the heating elements, comprising an external jacket and a number of internal coils, all heated by low pressure steam. Inspection of the heating coils inside the evaporators is possible and measurement data is available of their thicknesses by depth at various inspection intervals. This inspection data has been combined with operational data and thermal models for the heating elements. Our theoretical understanding from laboratory measurements suggests that corrosion is related to temperature through an Arrhenius relationship. As such we have been able to develop a predictive model for the thickness profiles and remaining useful life of the uninspected components. This model is a non-linear mixed effects (multilevel) model and has undergone significant developmental work to account for a number of practical data issues. This paper will briefly outline the various components of the model, whilst discussing issues relevant to any statistical model such as complexities of data collection, approaches to handling correlated data, selecting appropriate model formulations and data transformations. The inclusion of uncertainties in prediction via Monte-Carlo simulation will also be discussed.
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Nayak, Sandeep, and Reinhard Radermacher. "Thermoeconomic Simulation of 27 MW Campus Cooling Heating Power (CHP) Plant." In ASME 2004 International Mechanical Engineering Congress and Exposition. ASMEDC, 2004. http://dx.doi.org/10.1115/imece2004-60804.
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This paper describes the modeling of a 27 MW combined cycle cogeneration plant with 10,000 tons of cooling made available as chilled water at the central cooling facility that was designed and is currently operated to provide heating, cooling and electricity to the University of Maryland campus. The topping cycle of the combined cycle cogeneration plant consists of two gas turbines each producing 11 MW of electric power at full load. The energy of the exhaust gases from these gas turbines is then utilized to generate steam in two heat recovery steam generators. The heat recovery steam generators have supplemental duct firing using natural gas to meet the peak steam load. In the bottoming part of the combined cycle, the steam from the heat recovery steam generators is expanded in a backpressure steam turbine to supply steam to the campus at about 963 kPa, generating an additional 5.5 MW of electric power in this process. There is no condenser wherein the campus acts as a sink for the steam. The central cooling facility is designed to supply 10,000 tons of cooling as chilled water out of which 3800 tons is supplied by two steam driven centrifugal chillers, which utilize a part of the steam supplied to the campus and the remaining by the centrifugal electric chillers. The combined cycle cogeneration plant along with the central chilled water-cooling facility is modeled using a commercially available flexible cogeneration software package. The model is built based on the design data available from design manuals of gas turbines, heat recovery steam generators, backpressure steam turbine and centrifugal chillers. Two energy or cost savings opportunities were evaluated using the cogeneration software model. The first is adding inlet air-cooling using either an absorption or electric chiller to increase electrical power output during hot weather. This assessment included estimating kWh savings over a range of ambient temperatures. The second opportunity is using economizers to provide free cooling and reduce the usage of the electric and steam driven chillers. Detailed results of the thermal energy savings as well as the electrical and natural gas cost savings by employing these technologies are discussed in this paper.